It is known to transmit laser radiation in the range between 250 nm and 11 .mu.m via optical light-wave conductors such as wave guides and to process materials therewith in the widest sense. These applications also extend into the area of medicine.
It is likewise known that the effective portion of the applied laser energy in the actual target volume can be controlled only with great difficulty in heterogeneous materials because of multiple scattering at texture boundaries. For this reason, a work result can be estimated only with difficulty for a given laser energy.